An atypical case of recurrent carotid body carcinoma in a young adult dog: Histopathological, immunohistochemical and electron microscopic study

Abstract

A 3.5-year-old female Chihuahua was presented with complaint of neck pain, intermittent cough and dysphagia. Physical examination and diagnostic imaging of neck region revealed a solid and highly vascularized mass involving the retropharyngeal region. Histologically, the mass showed an atypical zellballen pattern which comprised of high density of type I chief cells with high nuclear cytoplasmic ratio and separated by delicate fibrovascular stroma. Immunoreactivity for neuroendocrine markers was diffusely positive in cytoplasm of tumor cells. Disseminated tumor emboli in external jugular vein were detected 6 months after initial surgery. An electron microscopic study revealed numerous electron-dense intracytoplasmic neurosecretory granules. Based on these findings, carotid body carcinoma was diagnosed.

Fig. 1.

Carotid body carcinoma; dog. Transverse computed tomography image at the third cervical vertebra revealed mass (asterisk) adjacent to the left side of larynx, displacing left common carotid artery and left jugular vein laterally (arrowhead).

Fig. 2.

Carotid body carcinoma; dog. The atypical zellballen pattern showing high density of type I tumor chief cells with high N:C ratio, and indistinct cell borders are divided into lobules by differing amounts of fibrovascular stroma. Pyknotic nuclei were commonly found among the high density of tumor cells (arrows). Hematoxylin and eosin (HE). Bar=50 µm.

Fig. 3.

Carotid body carcinoma; dog. Expression of synaptophysin showing many granules in cytoplasm of tumor cells. Adjacent blood vessel revealed intravascular synaptophysin-positive tumor cells infiltration (arrow). Immunohistochemistry for synaptophysin. Bar=100 µm.

Fig. 4.

Carotid body carcinoma; dog. Double immunohistochemistry staining for von Willebrand Factor VIII, visualized using DAB in a HRP system (brown stain) (arrowheads), and CrA, visualized using Fast red II, in an alkaline phosphatase system (red stain) revealed evidence of invasion of tumor cells (arrows) through the basement membrane of the blood vessel. Bar=100 µm.

Fig. 5.

Carotid body carcinoma; dog. Six months after initial surgical resection, recurrent carotid body carcinoma disseminated into the external jugular vein. Histopathological findings revealed atypical zellballen pattern with high type I cell density and numerous pyknotic nuclei (arrows). HE. Bar=100 µm.

Fig. 6.

Carotid body carcinoma; dog. Brain metastasis. Transverse images of magnetic resonance imaging at caudal brain area revealed a hyper-intense mass (arrows) involving left ventral cerebellum and left dorsal pons.

Fig. 7.

Carotid body carcinoma; dog. Electron microscopic study of carotid body carcinoma revealed electron dense neurosecretory type granules (arrow). TEM. Bar=1 µm.